A high-resolution neutron powder diffraction study of ammonia dihydrate (ND3⋅2D2O) phase I
Bibliographic record
Abstract
We have measured the thermal expansivity of ammonia dihydrate (ND3⋅2D2O) phase I from 4.2 to 174 K at ambient pressure, and the incompressibility at 174 K from 0 to 0.45 GPa, using time-of-flight neutron powder diffraction. The unit cell volume as a function of temperature, V(T), was fitted with a Grüneisen approximation to the zero-pressure equation of state (with the lattice vibrational energy calculated from a double-Debye model fitted to heat capacity data) having the following parameters at zero pressure and temperature: V0,0=356.464±0.005 Å3, (K0,0/γ)=7.163±0.024 GPa, and K0,0′=5.41±0.33 (where VP,T is the unit cell volume at pressure P and temperature T, KP,T is the isothermal bulk modulus, KP,T′ is its first pressure derivative, and γ is the Grüneisen ratio). The two Debye temperatures are θDA=165±3 K and θDB=729±4 K. The unit cell volume at 174 K as a function of pressure, V(P), was fitted with a third-order Birch–Murnaghan equation of state having the following parameters: V0,174=365.69±0.16 Å3, K0,174=7.02±0.25 GPa, and K0,174′=9.56±1.28. The volume thermal expansion coefficient, αV, at 174 K and atmospheric pressure is 281.3×10−6 K−1. The proton disorder manifested at high homologous temperatures is seen to be frozen in, on the time scale of these experiments, down to 4.2 K. A high-pressure polymorph of ammonia dihydrate was observed following melting of the sample at 179 K and 0.46 GPa.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".